Coal burning stoker



Feb. 9, 1932. v BANFlELD 1,844,026

COAL BURNING STOKER Filed July 3, 1928 Patented Feb. 9, 1932 PATENT OFF-ICE THOMAS H. BANI'IELD, OF PORTLAND, OREGON COAL BURNING STOKER Application filed July 8, 1928. Serial .No. 290,197.

This invention relates generally to coalburning stokers, and particularly to that type known as underfeed stokers employing crushed fuel which is deposited in a magazine and fed upwardly into a retort.

The main object of this invention is to provide a special form of fuel feeding mechanism which will prevent an tendency on the part of the stoker to gas or ust back through the fuel magazine into the furnace room.

The second object is to simplify the means for preventing such gassing and dusting of the stoker.

The third object is to eliminate entirely k 5 the escape of dust from the magazine, as well as to add to the appearance of the magazine itself. I

These, and other objects, will become more apparent from the specification following as ,39 illustrated in the accompanying draw1ngs,.

in which:

Figure 1 is a perspective view of a representative form of stoker showing the device attached thereto. Figure 2 is a view of a 5 somewhat modified form of stoker in which air is supplied to the fuel magazine. Figure 3 is a fragmentary vertical section through the magazine taken along the line 33 in Figure 2'. Figure 4 is a vertical section taken 30 along the line 4-4 in Figure 2.

Similar numbers of reference refer to similar parts throughout the several views.

Referring in detail to the drawings, there is illustrated the usual form of furnace front 35 10 in which is placed a retort 11 into which fuel is fed upwardly from the fuel duct 12 from the magazine 13, the feeding being ac complished by means of a worm 14 driven by a motor 15 through a transmission 16. While 40 coal 17 is being fed into the retort 11, air is also being delivered to the tuyeres 18 of the retort 11 by means of anair duct 19 to which air is driven by a fan contained within the casing 20, and also driven by the motor 15. The details of this mechanism are more clearly set forth in a copending application by C. J. Parker, et al., for a selective reduction gear, Serial No. 257,051.

A control lever 21 is provided for the air duct 19 by means of which a butterfly valve can regulate the supply of air passing through the duct 19.

A high pressure air pipe, or rather a high velocity air pipe 22 is carried from the fan casing to the top side of the fuel duct 12 and its connection 23 slopes in the direction zine 13 were they not otherwise prevented.

Turning now to my invention it will be seen to include a closure for the magazine 13 and means for admitting air to the fuel line, preferably the magazine itself. There is shown, for example, a closure 24 preferably bulging upwardly to clear the heaped up coals 25 in the magazine 13. The closure 24 is attached to the magazine 13 by means ofhinges 26 and its swinging end 27 can be held down by a clamp in the form of an eccentric lever 28, or-any other means which will hold the closure 24 firmly against the magazine 13. In order to insure an air-tight joint between the cover 24 and the magazine 13 a packing 29 is provided between same.

' While it is practical to employ this airtight cover in conjunction with the air supply pipe 22 (as shown in Fig. 1 is preferable to provide a direct air line, 30 from the fan casing 31 into the magazine 32. It is also desirable to provide the line 30 with a valve 33 and to protect the discharge outlet 34 of the line 30 by means of a screen 35 in order to prevent the air pipe from becomin obstructed by fuel.

ile it is desirable to have the various joints in the fuel duct air tight it is not absolutely essential that they be so, nor is it essential that any great quantity of air be delivered through the pipe 30 into the magazine 13. All that is necessary is that there be sufiicient to exceed any possible leakage and a sufficient balance to cause a slight flow of air in the directionwhich the fuel is moved. Owing to the fact that in common practice the fuel feed duct 12 is practically open to the atmosphere at each end and air is forced into the combustion chamber, it follows that any excess or unbalance of pressure must be on the side of the retort which would naturally cause a flow of air against the flow of fuel, but by closing the magazine end of 20 the fuel line and injecting air thereto, it

- naturally follows that the resultant flow of air must be toward the retort, and consequently the object aimed at in this invention is successfully attained.

It can thus be seen that by closing the fuel magazine 13 or 32 it will be impossible for gas and smoke to emerge from the fuel magazine while air is being delivered to the magazine-that is, while the stoker is operatingdue to the flow of air with the fuel, and it will also be impossible for gas or smoke to occur when the stoker is not being operated, due to the fact that the closure 24 is in place. Also if, for any reason, the magazine has been allowed to become completely empty, due to carelessness or oversight, and the stoker is operated by automatic controls, as is ordinarily the case, there will be no danger of the fire burning back into the fuel feed duct, as would be the case if no cover were in place.

I claim:

1. In a domestic underfeed stoker, a. retort, a fuel magazine having a filling opening at a convenient height for the householder to place fuel therein, an air and gas tight cover for said opening mounted for ready and convenient displacement for filling the magazine, a substantially horizontal air tight fuel conduit-leading from the magazine to the bottom of the retort, a conveyor within the conduit for discharging fuel to the retort from the magazine, a blower, an air duct leading from the blower to the retort, and means for operating the blower and the conveyor.

2. The method of preventing gassing in a fuel burner which receives its fuel thru a conduit thru which the fuel is forced by stoker mechanism and which receives air for combustion thru a passage independent of the fuel passage, which consists in sealing the fuel passageway except where it discharges into the burner so as to make it air tight, and in creating in the body of the fuel approaching the burner an air pressure greater than that existing in the fuel at the point of combustion.

3. The method of preventing gassing in a solid fuel burner which receives its fuel thru a conduit from a hopper and in which air is delivered thru an air duct to the combustion chamber from a blower; which consists in sealing the hopper so as to make it air tight and by-passing a. quantity of air from the blower to the fuel conduit in such a manner as to create a suction in the hopper and create inthe conduit between the hopper and the combustion chamber, a zone of greater pressure than exists in the main air passage adjacent its point of discharge into the combustion chamber.

4. The method of preventing gassing by a solid fuel burner which receives its fuel from beneath thru a fuel conduit from a hopper and which receives its main combustion air thru an air duct leading from a blower to the retort of the solid fuel burner, said air duct including no portion of the fuel conduit; which consists in sealing the hopper and fuel conduit so as to make them gas tight and in discharging air into the fuel conduit, at

such a pressure and in such a direction as to cause a flow of air thru the fuel conduit in a direction from the hopper to the burner, the pressure of the air in the fuel conduit near its point of discharge being sufiiciently great to drive the heat released volatile gases thru the burning fuel and also to furnish auxiliary air for combustion.

5. In an underfeed stoker furnace, a retort, a fuel conduit communicating with the retort, a fuel hopper, an air tight cover for said fuel hopper, means for delivering fuel from said hopper thru said conduit to said retort, a blower, means for conveying main combustion air from the blower to the retort, and additional means connecting the blower to the fuel assageway between the hopper cover and t e retort to create an air ressure in the fuel conduit near its point 0 discharge greater than the pressure of air at the point of combustion.

6. In an underfeed stoker furnace, a retort, a tubular conduit communicating with said retort, a hopper, an air tight cover for said hopper, a worm in said conduit for delivering fuel from the hopper to the retort, a tuyere bordering the retort, a blower, an air passage connecting the blower and the tuyere, and a pipe leading from the blower at the point of highest velocity of the air and injecting the air into the fuel conduit between the hopper and retort to create in the conduit a zone of higher pressure than exists in the retort.

7. In an underfeed stoker, a retort, a fuel hopper, an air and gas tight cover for said fuel hopper mounted for ready and convenient displacement for filling the hopper, a fuel conduit leading from said hopper to said retort, conveying means for moving solid fuel thru said conduit toward said retort, a blower, means for conveying main combusvtion air from the blower to the retort and means for conveying auxiliary air from the blower direct to the fuel hopper to cause a constant flow of auxiliary air from the'hopper to the retort the fuel conduit at such a pressure as to block any seepage of furnace gases into the room in which the hopper and blower are located.

THOMAS H. BANFIELD. 

